1. Field of the Invention
This invention concerns a CCD (Charge-Coupled Device) microscope for observing an object such as skins or scalps by projecting them at a predetermined magnifying ratio on a screen.
2. Related Art Statement
A CCD microscope for observing skins and like other objects under magnification comprises a CCD device, a lens system for focusing a magnified image of an object on an imaging surface of the CCD device and an illumination device for irradiating an illumination light to the object.
The surface state of skin such as skin roughening and texture can be observed by focusing a light reflected from the skin surface, and the inner state of the skin such as spot and dullness can be observed by focusing a light scattered in the inside of the skins while cutting off the light reflected on the surface.
Therefore, the CCD microscope of the prior art comprises two illumination systems, namely, a non-polarized light illumination system and a polarized light illumination system as an illumination device, and a polarizing filter is intervened in an optical path from an object to the CCD device. This filter functions as an analyser having a polarizing direction in perpendicular to the polarized illumination light of the polarized light illumination system (refer to Japanese Patent Laid-Open Hei 4-214523).
The polarized light illumination system comprises a light source for illumination of a polarized light and a polarizing filter as a polarizer for linearly polarizing the light irradiated from the light source. In the illumination light linearly polarized by the polarized light illumination system, a light reflected on the skin surface as an object and kept unchanged for the polarized state is cut off by the analyser before incidence to the CCD device and only the light scattered in the inside of the skin and changed for the polarizing direction enters the CCD device. Accordingly, spot and dullness in the inside of the skin can be observed by the illumination from the polarized light illumination system.
Further, since the illumination light irradiated from the non-polarized light illumination system is a natural light and includes all sorts of polarizing directions even after reflection at the skin surface, it enters the CCD device even if a portion thereof is cut off by the analyser. Therefore, the skin surface can be observed by the irradiation of the non-polarized light illumination system.
However, when the object is illuminated by the non-polarized light illumination system, the light after random reflection in the inside of the skin also includes all sorts of polarizing directions and, accordingly, enters the CCD device even if a portion thereof is cut off by the analyser, so that both of the surface state and the inner state of the skin, when picked-up, are displayed simultaneously to bring about a difficulty in the observation.
Further, comparing images obtained by illumination from the polarized light illumination system and those from the non-polarized light illumination system, since the illumination light from the polarized light illumination system is transmitted through the polarizer, it is dark as compared with the illumination light from the non-polarized light illumination system. Therefore, images obtained by illumination from the non-polarized light illumination system becomes entirely darkened, to thereby possibly cause an erroneous judgment of taking an area without spot and dullness for actual spot and dullness.
Therefore, the brightness of the illumination light of the polarized light illumination system was increased or that of the non-polarized light illumination system was decreased for adjusting the optical intensity of them, but entire images illuminated from the polarized light illumination system still appeared somewhat darker.
As a result of a further study made by the present inventor for making the cause clearer, it was found that the darkness of the images when illuminated from the polarized light illumination system is caused not only by the optical intensity but also by the difference of the color of the illumination light.
Then, when a color filter for adjustment of color temperature was used in the non-polarized light illumination system, and when comparing the images on the screen of both of the cases, tones of the entire screens were identical, so that erroneous judgment of taking an area without spot and dullness for actual spot and dullness could be avoided.
However, color adjustment by interposing the color filter was troublesome and, if the skin was illuminated by the non-polarized light illumination system and since, both of the surface state and the inner state of the skin were projected simultaneously even after color adjustment, the problem of the difficulty for the observation of the surface state was still left undissolved.